Wednesday, October 19, 2016
Valve Wizard Small Time
Here's Valve Wizard's take on the PT2399 delay. It's very similar to most PT2399 delays out there, with a dual op-amp providing input and output buffering. This was designed with the tails function and it uses Valve Wizard's usual J112 switching. Here's his original schematic and explanation of the circuit. You can also use a DPDT footswitch for bypassing, using one side to turn the delay on/off and the other for LED indication. I've included 2 extra pads on the PCB layout for this function. If going this route, don't populate the J112 along with the 1N4148 diode, 1k and 4.7k resistors, and 10µ capacitor round the J112.
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Verified this over the weekend. It sounds great! I used the original J112 switching style.
ReplyDeleteSo I slightly jumped the gun on this... The effect works and sounds pretty good. The long repeats are a little low fi, but that's ok.
DeleteThe switching circuit must be wrong somehow... The LED is on when the effect is off, and turns off when the effect is engaged. Furthermore, I get a pop when turning it off or on that goes through the delay circuit, so it's really noticeable. I haven't gone through the schematic to check for errors yet, but at a quick glance it looks right... Not sure why these things are happening.
J112 is backwards on the layout. Looking at valve wizard's doc confirms it.
DeleteSo, turning the J112 de right orientation makes it work well?
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ReplyDeleteWorks as it is in the schematic? Or do you have to change something?
ReplyDeleteHi, may I can use a 3pdt? I think that could do it TrueBypass... And have a good new year....
ReplyDeleteYou can. Just jumper the source and drain pads of the JFET.
Deleteif I put a 3pdt footswitch, I must populate the pads for diode, resistors and caps mentioned or not?
DeleteNo
DeleteHi, does it work with a j201?
ReplyDeleteIt should.
Deletethank you, in these days I try it!
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ReplyDeleteThis comment has been removed by the author.
DeleteThere seems to be 2 different schems on the link in the description (one on the page and the other in a PDF link) and there are a lot of differences between them. Anyone know which one is correct?
ReplyDeleteThe linked pdf seems to be a new version, though most of the difference seem to just be value changes, mainly in the JFET switching and one resistor leading to the repeats pot. The only other changes I noticed was changing the polarity protection diode method, adding a 10Ω resistor and altering the filter cap on 4.5v from 10µF to 100n (which seems a little weird to me). The layout above should work just fine as is. If you want to use the value changes of the new version, replace the 1k resistor off the Fsw2 pad with a 1M and the 10µF below that resistor with a 100n. The other value to change is the 10k resistor next to the 47nF cap on the left side to 8.2k. Not sure if these changes will really alter the sound all that much (the ones in the JFET switching certainly won't), so I personally probably wouldn't bother.
DeleteAahhhh, copy that. Built one on a vero board because I was too lazy to etch a circuit, but I found a handful of errors in the layout. Serves me right. Thanks!
Deletemost pt2399 works with pin 3&4 shorted to ground
ReplyDelete